Generally a vial is used in such a way that a rubber stopper press-fitted to the vial neck is covered with a cap, a predetermined portion of the cap is then removed, and an injection needle is passed through such removed portion.
In a conventional cap, a through-bore has been formed in the top plate of the cap main body made of metallic material and a resinous removable member has been attached on this through-bore of the top plate. When intending to open the cap, this removable member is raised up to break the attached portions thereof. With such arrangement, however, the attached portions may not be provided with good airtightness and it is not possible to heat-sterilize the cap with the removable portion remained as attached to the cap main body, since the removable member is made of resin. Accordingly, such cap has not sealingly been fitted in the aseptic condition to the rubber stopper and subsequently the rubber stopper portion through which an injection needle is passed, has not been covered in the aseptic condition. This has required a sterilization method other than heat-sterilization, so that complicated and therefore expensive sterilizing equipment has been necessary. Moreover, since such conventional cap comprises a metallic cap main body and a resinous removable member, complicated manufacturing equipment has also been required.